Choosing Eyeglass Lenses: By Feature
In addition to being available in different lens materials, eyeglass lenses are also available with different design features. Two popular types of eyeglass lenses are photochromic lenses and progressive lenses.
Photochromic lenses are sun-sensitive lenses that darken outdoors and lighten to a clear lens indoors. The most popular brand of plastic photochromic lenses are Transitions lenses made by Transitions Optical (Pinellas, FL). Transitions lenses are available in gray and brown sun-activated tints. The most popular glass photochromic lenses are made by Corning Ophthalmic (Corning, NY), and are called PhotoGray and PhotoBrown lenses.
Photochromic lenses offer the convenience of having one pair of eyeglasses that can also act as sunglasses when you step outdoors. However, these lenses need ultraviolet (UV) light to activate their tint, so they may not darken as much as you want them to when you are inside a car. (Today's auto glass blocks most if not all of the sun's UV rays.) For driving on sunny days, you still may want to purchase prescription sunglasses.
Progressive Addition Lenses
Progressive lenses are for individuals over age 40 who are becoming presbyopic (losing their near vision due to aging changes in the eye). Also called "progressives," these lenses are similar to bifocals because they have a distance and near prescription in the same lens. But progressive are unique because as your eyes look further down the lenses, there is a progressive increase in up-close focusing power, until the full near prescription is reached. This continuum of lens power provides a natural range of vision for seeing objects at all distances.
Most people today who need a bifocal prescription choose progressive lenses. In addition to providing a more natural range of vision, progressive addition lenses have no visible lines and give the wearer a more youthful appearance, compared to bifocals.